Special Senses Vision

Structure of the Eye

Before reaching the photoreceptors on the retina, light must pass through the optical apparatus that is made up of the cornea, aqueous humour, lens and vitreous humour. The globe is protected by the sclera, which becomes transparent in the anterior part of the eye known as the cornea (Figure NE.9). Aqueous humour is produced by the ciliary processes and catalysed by the action of carbonic anhydrase; it passes from the posterior chamber through the pupil into the anterior chamber of the eye. It is then drained into a vein via the canal of Schlemm (located at the angle of the anterior chamber). Pupillary size is determined by the activities of the smooth muscle fibres in the iris: the circular fibres constrict (miosis) while the radial fibres dilate (mydriasis) the pupil. The interior surface of the globe is lined by the retina, except where the optic nerve leaves the eye and where the ciliary muscle begins. The ciliary muscle changes the tension of the suspensory ligaments that alters the convexity of the lens and thereby achieves accommodation.

fwn discriminative touch propiog ft ion temperature fwn discriminative touch propiog ft ion temperature

Figure NE.8

Somatic sensory perceptions and their afferent pathways to the CNS

Figure NE.8

Somatic sensory perceptions and their afferent pathways to the CNS

Figure NE.9 Structure of the eye
Dealing With Impotence Naturally

Dealing With Impotence Naturally

Put an end to the disappointment, frustration and embarrassment of... Erectile Dysfunction. Have Sex Like You are 18 Years Old Again. Have a natural powerfully stiff penis. Eject volumes of semen. Do it again and again night after night. Never make another excuse for not being able to get it up.

Get My Free Ebook


Post a comment